Chip breaking attachment for drilling machines



De.l2s,194s. vM C. TAYLOF; 2,457,"7v95 CHIP BREAKING ATTACHMENT FOR DRILLING MACHINES De.28,194s./ M, QTAYLOR 2,457,795 I CHIP BREAKING ATTACMENT FOR DRILLING MACHINES Filed Sept. 17, 1945 Dec. 21s, 194s. I M. C TAYLORI 2,457,795

CHIP BREAKING ATTACHMENT FOR DRILLING MACHINES Fwiled sept..17, 1945 l 5 sheets-sheet 5 NVENTOR.

Patented Dec. 28, 1948 CHIP BREAKING ATTACHMENT Fon vDRILIJING MACHINES.

'Miltcni Taylor; Chicago, Ill;y assigner;.byymesnev assignmcntsatolxeCell- (lk-(l.orporatiern Detroit, Mich., acorporation of Michigan.vv

Application September 17, 1945 SerialfNo. 616,801

i61aims.

The present invention relates to the'v art of drilling a hole in machinable material'ssucli as metals, alloys, elastomers and plastics whichis usually done with twist drills or the like and more particularly to an improved construction foraccomplishing the Karweit drillingY process de'- scribed in application Serial No. 484j612 filed April 26, 1943, now Patent Number 2,453,136, reference to which is hereby made-for-afurther v explanation of the Karweit process, which briefly stated, is a process in which a drill such as used in the metal and plastic art is repeatedlyoscil.- lated Within a minor portion of a revolution Once approximately each revolution of the drill t-o comminute the chips so that they will pass out of the flutesv of the drill quite easily without scoring the side walls of the cut orjpacking in' the utes.

The present invention is also an. improvement in certain respects uponmy earlier. application Serial No. 572,710 iiled January 13'; 1945 relating to the same subject matter, reference to whichis hereby made for a detailedv discussion ofA the merits and `results obtained. by using a planetary type driller to time the frequency of oscillation in stepped relationship. tothe rotationoi" the. drill whereby the oscillation. canbe arranged-to. occur once approximately every three revolutionsor. at any other ratio desired within the limitsof. the Karweit` process.

One of the objects of the present. invention-is to provide an improved'arrangement for, oscillating the drill during a feed traverse thereof .in Which the rolling parts of the oscillator. carry only a part of the feed load developed in feed traversing the drill throughout. its cycle of operation.

Another object of the invention is` to utilize the effect of centrifugal force to augment-the resilient means by which a cam and followeroftbe oscillator are urged into engagement at the higher speeds at which the follower is more likely to float without following the relief contour of the cam.

A further object of the invention is to provide a driller of the type hereindescribed which cansbe readily changed to vary the frequency ofl operation in relationship to drill rotation as by changiner the gear ratio which controls the=frequency of operation, or, by eliminating: ageardrive entirely.

Another object of the invention is toprovidean improved construction in which moments Iof inertia force involved in oscillating a drill toperform the Karweit processarebalanced against face.

. 2 each otherrto reduceoscillation or Ahainmeringiof the-spindle bearings ofthe` drill .pressi Aeiurther.y obi ectfzof; the invention isl .to provide ari-improvedl contructionwto perform: the Karweit drilling process which is. inexpensive to ioperate; service andi maintain` and` easily: comprehended and usedby drill press operators.`

These beingiamonfg theobjects ofi the-.present invention other? and` further# objects willi` become apparent from the drawings, the description relating' thereto 1 and the appendedvv claims.`

In the: drawings Fig. I is aside elevation of? a. handeeddrill press upon the quilloff'whiclianyV one vofi the embodiments `describedhereinflsumounted Fig.` 2' is an` enlarged? vertical lsection of lth'e deviceshown in'l Fig. l illustratingonefoirnaof4 the invention.

Figi. :3f-is a section taken upon'.the line 3"--3lin Fig'. 2;

Fig. 4 is` asection taken upon thelineML-l in Fig. 2.

Fig. 5 flaany enlarged vertical #section similar to Fig. l2 illustrating anotherform ofthe-invention.

Fig," Gris` a sectiontaken upon the lineef-if of Fig. 5I

Fig;`V 71 islam-enlarged verticalsection taken- -ofa driller-similar tothe formshownzinl-Figs. 1l ari-d5 illustrating another form ofthe-dnventionwlii'ch can be'V used forl high speed:` drilling witlli-V drills smaller than 1A".

Eig. lllisaa planviewpi the device illustrated in Fig. 7, and

Fig. 9iis.aplan viewfof theimprovedivaneand followers carriery shown in Fig; 7E for dissip'ating heat developed bythe embodimentI showndnwFig. 'Tlwhen operatingvat l'ii'ghfspeeds.`

Although various means have been employed heretofore-to i accomplish@ the Karweit process; of drillingy a1 stringymaterial witha twist drill,` all of there` have virtually involved rolling a-follower in a circular `path-uponaf-ilat or planary carnsur- Withthese constructions, centrifugal thrust uponthe followers; whichhavecbeen rollers ory frictionless bearing elements, has caused fwear and developedy heat particularly when subjected tothe-'heavy loads. that are carriedr by the= cam and followerr arrangement in' transmitting the feed thrust` fromr the drill spindlei to' the; drill. Furthermore, with the arrangement heretofore employed the rolling elements" of the followers have preferably been rounded' tou reduce the scuflin'gfeffectexperiencedwitha-cylindricaltread surface v-rollinginea curvedpath onA a planar surface. With the rounded; rollerb thel pressure factor per Isquare inch contact was quite high and excessive loading of the driller by inexperienced operators became a problem because of the extra heat generated and the excessive wear incurred due to this abuse and also the failure of the operator to keep the device properly lubricated.

Not only this, but a spring strong enough to assure that the follower would follow the relief in the cam at high speeds would be an unnecessary additional load upon the cam and follower arrangement at lower speeds.

In the present invention these problems have been overcome by rotating cylindrically treaded followers inside of and against a cylindrical cam path so that the load factor per square inch is lowered by distribution thereof over a line contact. Furthermore the centrifugal effect upon the followers at higher speeds augments the spring action which is provided to urge the followers to follow the cam relief contour. In doing this, I preferto transmit the main portion of the feed thrust pressure upon a drill through a fulcrum with the followers mounted on the long arm of a lever to thereby further reduce the loading upon a cam and follower arrangement. Thus through a load relieving lever the cam and follower arrangement has a force advantage and also complete-control over the feed thrust pressure. 1

By way of illustrating my invention and its use, a drill press l is shown in Fig. l in which a drill press head Il is mounted upon a standard l2, to carry upon one side of the standard a motor I3 and upon the other side a quill I5 which is driven from the motor through the belt and pulleys ifi. The quill l5 is reciprocated for feed and return movements through a rack and gear (not shown) as controlled by a manual throw or handle I6 and carries on its lower end a chuck I1 having a Morse taper that receives a shank I3v of a driller embodying the invention. The driller 20 in turn is provided with an Erickson chuck 2| receiving a twist drill 22 in rotary drive relationship to cooperate upon a work piece 23 that is mounted in turn upon the table 24 of the drill press. A lubricant line l25 -is provided with a 'ilowsof lubricant supplied to cool and lubricate the drill in its drilling operation. If lubricant is employed it can also serve to wash away the chips formed by the driller 20.

v As more particularly shown in Fig. 2 the driller 20 comprises an outer casing composed of an upper portion Z6 and a lower portion 21 which are secured together .by bolts 28 and supported yagainst rotation by an Outrigger or arm 30 resting against and sliding up and down on the standard I2 during feed movement of the drill.

As shown in Figs. 4, 7 and 8, the Outrigger or arm 3l) is secured to the upper portion 26 of the 28 the portions define an interior compartment within which the working parts of the device `are housed protectively and lubricated. An opening 34 in the upper portion receives the drive member 35 and the wall of an opening 36 in the lower portion 2'! receives in journalled relation ship a driven member 31. I y

vshoulder 6l on the driven ymember 3l.

The drive member 35 includes the shank I8 which mates with the Morse taper il' in the usual manner. When mated the rotary and feed drive of the spindle is transmitted to drive member 35.

In order to transmit the rotary drive of the drive member 35 to the driven member 3l, the drive member is bored out as at 38 to a cylindrical contour and slotted at diametrical sides to the wall thereof as at L30.

The driven member 3l is externally grounded at its upper end to telescope into the cylindrical bore 38 of the drive member and receives a pin 4l therethrough whose outer ends extend outwardly through the slots t@ in the drive member. With this arrangement the rotary drive of the drive member 35 is directed against the pin 4l by the walls of the slot 40 and the pin A! in turn rotates the driven member 3l. The length of the slots 40 is such that the drive and driven members may be reciprocated with respect to each other.

'I hefeed thrust from the drive to the driven member is transmitted through a mechanism housed in the casing which mechanism also accomplishes the reciprocation of the driven member to impart to the drill the oscillation desired as prescribed in the above mentioned Karweit application and known as the Karweit process. This mechanism comprises two vertically spaced, substantially identical rings 42 having a cam path on their inner face which includes a cylindrical dwellportion [i3 (Fig. 4) and sinoidal relief Mi of from .015 to .040 of an inch in depth extending over an arc from 40 to 60. The rings 42 are inverted with respect to each other and have their respective reliefs displaced with respect to each other to define two vertically spaced cam paths with the reliefs diametrically opposite each other. These rings rest against a shoulder 45 in the upper portion 26 of the casing where they are supported against rotation by pins lili. Sufficient clearance is provided radially around the outside of the rings and between them for them to hunt slightly in balancing their load to allow for certain manufacturing tolerances permitted in the mechanism.

Rollers lll having cylindrical treads thereon are provided to roll against the cam tracks of the rings as supported upon journals d8 provided at thetop of levers 5D. The rollers are held in place upon the journal by a washer assembly 5l and a pin 52 to rotate against a positioning shoulder 53 upon the levers 50.

The levers 50 in turn are mounted upon a carrier 5t by pins 55 which serve as fulorums. Although levers are mounted to operate as class one levers, other classes of operation can be employed as long as the long arm of the lever carries the followers and the short arm carries the 'main portion of the load for the fulcrum. In

the particular embodiment shown. the short arm is nothing more than a square contour indicated at 56 which operates almost like a cam against the outer race 5l of an end thrust frictionlcss bearing 58 whose inner race 60 rests upon a A spacer may be substituted for the frictionless bearing 58 in the embodiment shown in Fig. 2 since there is no relative rotation between the carrier 54 and the drive member 3l in this embodiment. However, the frictionless bearing is preferably illustrated since with it mounted in place the construction shown can be converted to a planetary control- Aof the carrier 53 which conversion is shown in Fig. 5 as will be hereinafter described.

amg-zeen-positionngthe;.-oscillatingrmeelianismifavon-.

ably; for.` its.` operation,V al. shoulden 62"; upomthe. drive member-35 receives'..the inner racefiof. ai frictionless bearing 64IV whiclrsupportsf. the casingfl portions 26" in.` journalled: relationshipgupon theA drive member. Below: the innerfraiceaiaispacer 65 is mounted;againstawhichzthecarrier 54:. With this arrangementia.positlvevlinlragevisipro vided between the drive; member.y I8'. and. the driven member: 31.- to. carry the: axial end-:thrust:v or feed pressures to.. which. the systenn is. sub:- jected; This linkage .starts'witliV the: shoulderil'y upon` the drive member and ends. with; thez shoulder yGli upon; the, driven;.memben and; im` cludes the inner;l racel 6:3, the bearing; El; the. spacer.v 65, the carrier; 54;.the pivotzpimorf-fulcrum; 55, the short arm/5610i:` theV lever: andi the fric:` tionless bearing 58.

This linkage is;l urged to; maintaimsolid, conel tacts throughout. byA apcompressioni'springi 66; one end of which; rests` upon@ the shoulder' 65|; formed` integrally with: the. Spacer 6i andA the; other end o1". which engages: a; flangedlwasher 68f which rests against the pin tal; 'Ilheangetsover the ends of. the pin,k and holdsthepin" inv position. l

Rotation of the carriere' 5ba, Wfth: the: Adrive-i` mem-:- ber 35 is establisl'ied. by keys-v 'l'locatedr in key.' ways 'H andv 'I2 upon-thefdrivemember andthe carrier 58, respectively, as more particularly shown in Fig. 3;

The ring members 42 are-held in place-by means of a Washer 13 supportedupon; aspacer lll which also locates-.thetwofparts oithecasi-ng; with respect to f each; other,` iii-:mutual r alignment.

l A seal,1=5of ak conventionaltypeis provided in the bottom of` the casing toprevent` any lossof lubricant from the casing,.the casing' being lled with light oils such as- W( S.A-.ll.v to.A the height of thepin 55isothatthelcarriery` 54 will causeA the oil to splash" and bathethe4 fol.- lowers without causing undueagitation of1u. bricant, in the casing that. would, develop. v` any appreciable heat.

From the invention thusk far. describeddtwill. be seen that thedrill will. he lifted a,sl'1or.t` di'stance onceA approximately each, revolution; with the embodiment described dependingv upon. whether or not thework. pieceis stationary orr rotated; The distancethedrill isliftedis determined byy the depth of thereliefLon the ring cams 42. The deptliof thisrelieiisdetermined in relationship to the maximumexpected feed traverse to be used with the driller andthe lever ratio present so thatthedrillwill be.y lifted just enough for the cutting edges fto cutfi'eerom the work piece and terminate the. chips, being formed. As mentioned in' tl'ieear1ierl Karweit application it is preferredlthat theextradistance of lift be enough to allow for deflection experienced with the drill' headand to have the drill come free farv enough from its workfor'tlie lubricant supplied by1 the lubricant nozzle 25A` to bathe the lcuttingedges ofthe-tool` Otherwise the distancefor the lift'f of'tlie drill`-witliin a minor portiorrof a revolutiim as thus'prov-ided should be kept; at a minimum to' reduce asfmuch as possible the inertia.,moments?n involvedA in reciprocating' the driven. member. once approxi#- rnately each` revolution;

Referring to Fig. 5, like;partswareaindicatednby like numerals and the.descriptiorrhad:Lthereofiin connection with Fig. 2 applies also to Fig..5j';.

In Fig. 5the spacerrw is; removediandatlie ring gear- 6..,of a planetaryasystemxiof:..gearine; .1.1L is.

6?! rigi-dlyfelena-pede:lietiimen` tneitwospmtions Mandi 21 of the casing asiheld:againstzrotatiombwamim 18. 'Ilhekeystiarew dispensed withzandtheisun gear 8 lli of f the plzametairyrgearing` is?. keyed'E to.; ther i drive` member' 35i through.. the-slot:I lili which, will2 be seen. extends upwardlyfa; distancesuicient .fon this purposes This; arrangement; leaves: tine` carrier. 5w; free: to'rotate aszarp independenufbody. andii'ts mme-i tion is:controlledrby thezplanetcgears 8511i mig. (if)Y in relationship; tor.- tlie'. interaction therewith; of; the` sun-geanwhicht rota-tesi at drillA spreedi andi the ring gear: Tft which is; stationary havingih m-indi the relative gear ratio of the@ gearing; mentioned ini myrpreviiousaapplication; this-.raum isf; preferably: such"k that. ai drill oscillation; will;L occur: once ,approximatelyseach 1%-, revoluttonszofi theidrillj. ther-relief upontxhegcamibeinglgshortenec sufficiently; that apprrnzimately'Au the'v 60?* of: are, providedi in the .other embodiment-,is:l rnainiuilnedil in.` efectifor the drill in .this-1 embndirirent'.A

In viewing Fig: 6 itawill bey ratherrapparent that2although'the1size of the sungeanwillinoti be varied: very'` rnucln thetsizei of. theeringf gear; cani be, and planet: gears cans be of.' differenti sizes to:` varyzf the periodicityl of:= the reciproeationi ofi theI drill inrelationship: to its; rotation...

The carrier 54a moves. with. the:` planet 1 gears.. since theshaits'. 82; upon which they;- are journall'ed arezrigidlycarried byvthe. carrienla; the two a planetzl gears i being;locatedi diametrica'llyi opposite eachy other:y at-zrightv angles; to the@ toll lowers so that. the slot'si 831 ini which` the followers slide mayserve asi-guideways fori the==lorig-^arms of the levers to maintainthe-.followers.attdiamete rically` oppositel points.- IfS desired;y the shoulder 67.- uponi they spacer 65-may be eliminated .to pro-` videf a., smoothrsurfacedV spacer 55a. and;l in` lieuk thereof; a. floating washer:` 8l can be provded which rests. .'igainstuthe upper` face of the: sun` gear a0: Gilitenwasher 845'. and hardened-thrust washerfi transmit;y thefeedl pressure. existent between:y theI carrier 54uand the spacer 65' through the body of; the sunl gear SEL-: In order.I

to provide 1 the` mos-t" favorable cooperation. bem

tween these washersi the-upper one, M1; is keyed" toi the drive ,vshaitfwhile' Athe lowervoneA 85 i free to slip againstfthef. carriers Slat or.' the uppers' one' Niorsboth;

Referring.' to Eig; an erriliodinent,isslflownk inwliichfthe compression spring. l-lwhichiurges thedrive member -35atandi a; driven 1. men'lbery 31u` towardsV eachotlier.- is located insidethe driven member` for reasons offcorrrpactness.V Tlieaspring` Illll rests in aE metal-cup. i011.; the lovverfenclicxfE which engagesr af..pin` H125.y rigidly carriediby:` the drive member 35a and the otherrendiof the spring engages a pint |532 rigidly: carried b-yi the driven member 31a. TheI pin. |53 is.r freedoff: restraint from the cup, |0 I byvfa:- slot; l 0I: The; pins are driven into'. place;Y through: suitably aligned openings'and the pin; |021: passes throughlongi'- tudinally elongated? slotsa in they drivenmember lila... The follower` carrierl El'h inthisi-` embod` ment is rigidly 'f carried by; the'drive memberA 35a' with; the pinsf 5.5":1.l supporting.' the leversna.; dis, posed:V belowr the: shoulder 6I a: to make; classer two leversnofv them; With this .arrangement a1 longer4 lever-arm can be provided?tofsupporttthe fol-- lower 41h in. engagement Withringj camst Wa without sacrifice: tocompactnesst Veins.y R55 are provided` at the peripheryffofthe carrier No and the:V casing i 319i: provldedzwith' au cylindrical wall llwhiclrserves as aisliroudffon theffan -bywliich airizis-:drawnldown tl-iroughiinlets-ifi-n theupper 7 part of the casing and forced downwardly from the shroud |06 towards the work.

The ring cams 42a are supported loosely in place by bolts 46awithin a recess |08 of a cap H which floats loosely upon a conical surface lll that is provided upon the upper face of a flange l l2 form-ed integrally with the drive member a. The carrier member 54h has an external flange H3 at the top thereof which runs against the bottom face of thering cams 52a with the .upper face of the ring cams engaged by a lubricant washer lill disposed below the flange H2. With this arrangement the ring cams 42a are positioned with respect to the drive member 35a and since thering cams 42a carry the casing 39a through bolts 46a, the whole assembly is a semifloating assembly which does not provide any thrust loads that require conventional frictionless or end thrust bearings, the oscillating load being dissipated .radially against ring cams through rolling conta-cts provided by the rollers 41a against the face of the cam. The only end thrust carried by the relative members other than through the pin a against the reaction of the cam at the follower assembly is vthe weight of the casing and since this is negligible, the device thus provided` when operated at high speeds runs comparatively cool.

The cap Nilis provided with an oil reservoir H5 .which is iilled with waste or felt |I6 and has a wick Il l leading therefrom to'discharg-e oil in minute quantities down through a drip opening H8 in the washer H4 from the bottom of which the oil is picked up by the rollers 41a. as they pass thereover in their rotation.

Having thus described the invention in its several embodiments it will be seen how the end thrust load is dissipated in a radial direction that is entailed with oscillating the drill according to the Karweit process. Furthermore the increasing I centrifugal force engendered vby the followers with higher speeds counteracts the tendency for the follower to float over the relief in the cam which also increases at high speeds. Thus a lighter spring can be used to urge the drive and 1 driven member toward each other. Not only this, but the ,moments of inertia involved in reciprocating the elements are greatly reduced. f f

Consequently, although several preferredem-l bodiments have been disclosed and described herein it will be readily Iapparent to those skilled in the art from the description and Ydiscussion herein made, that various and further modifications can be made without departing from the spirit of the invention, the scope of which is commensurate with the appended claims. What is claimed is: i y 'i 1. In a device of the class described having a housing and a drive shaft and a drill carrying driven shaft mounted therein for simultaneous rotation and relative reciprocation, anY annular cam member supported upon the housing and having an inside cam path thereon with a relief therein occupying a minor portion of the circumference, a fulcrum member supported upon the drive shaft and rotatable therewith, a lever mounted upon the fulcrum member and having a follower` upon one arm thereof engaging the cam, and means for transmitting movement of Ythe other arm of the.lever to the driven shaft whereby the driven shaft is reciprocated axially once each time said follower moves across said relief a distance sufcient to comminute chips developed bytheydrill when the drill is in cutting position. l 2*. In, a, Ndevice, o f ,the class ,described having drive and driven shafts supported for simultaneous rotation and relative reciprocation, said driven shaft being adapted to carry a drill, a pair of annular cam members supported upon the housing and each having an inside cam path thereon with a single relief in each occupying an arc of less than fulcrum members supported upon the drive shaft and rotatable therewith, levers mounted respectively upon said fulcrum members and each having a follower upon onearm thereof, said followers respectively engaging said cam paths, and means for transmitting movement of the other arm of each lever to the driven shaft whereby the driven shaft is reciprocate axially once each revolution a distance sufficient to comminute chips developed by the drill when the drill is in cutting position.

3. In a device of the class described having drive and driven shafts supported for simultaneous rotation and relative reciprocation, said drivenshaft being adapted to carry a drill, an annular cam member supported upon the housing and having an inside cam path thereon with a relief therein occupying a minor portion of 360,

T' a follower, means for supporting the follower in contact with the cam path, means for rotating the supportingmeans in stepped relation with the drive shaft and means controlled by the follower andl cam member for oscillating the driven shaft in stepped relation with the drill rotation a distance sufcient to comminute chips developed by the drill.

4. The apparatus called for in claim 3 including a blower for moving air over and in direct contact with the follower and cam.

5. In a device of theclass described having a stationary element and a drive shaft and a drill carrying driven shaft journalled for simultaneous rotation and relative reciprocation, a cam and follower assembly including an annular cam member supported on the stationary element and having a radial cam path thereon with a relief therein occupying a minor portion of the circumference, a follower member supported upon the drive shaftand rotatable therewith to cooperate with the cam memlber, means for urging the members into contact with each other, and means for translating movement of the follower member to oscillating movement of the driven shaft whereby the driven shaft is repeatedly reciprocated axially a distance sufficient to comminute chips developed by the drill, centrifugal force augmenting said urging means at higher shaft speeds.

`6. Ina device of the class described having a stationary element and a drive shaft and a drill carrying driven shaft journalled for simultaneous rotation and relative reciprocation, a cam and lfollower assembly including an annular cam member and a follower member cooperating with each other for relative radial movement with the cam having relief therein occupying an arc of less than 180, one of said members being carried by the stationary element and the other member being supported upon the drive shaft and rotatable therewith, means for translating the relative radial movement to an axial movement including a lever, and means controlled by said lever for reciprocating repeatedly the driven shaft axially in stepped rotation therewith a distance sufficient to'comminute chips developed by the drill.

. 7 The combination called for in claim 6 wherein said translating means reduces the distance of axial movement to less than the distance of the relative radial movement. i

8. In a device of the class described having a housing and drive shaft and a drill carrying driven shaft mounted therein for simultaneous rotation and relative reciprocation, the combination of an annular cam member supported upon the housing and having an inside cam path thereon with a relief therein occupying an arc of` approximately 60, a fulclum member supported upon the drive shaft and rotatable therewith, a lever mounted upon the fulcrum member and having a follower upon one arm thereof engaging the cam member, and means for transmitting movement of the other arm of the lever to the driven shaft whereby the driven shaft is reciprocatecl axially once approximately each revolution a distance sufficient to comminute chips developed by the drill when in cutting position.

9. In a device of the class described having a housing and a drive shaft and a drill carrying driven shaft mounted therein for simultaneous rotation and relative reciprocation, an annular cam member supported upon the housing and having a radially disposed cam path thereon with a relief therein occupying an arc less than 180, a ring gear carried by the housing, a follower device cooperating with the cam member including a lever and a cam follower on one arm of the lever, a planet gear carried by the follower device in mesh with the ring gear, a fulcrum member supported upon the drive shaft and rotatable therewith, means for translating radial movement of the lever to an axial oscillation of the driven shaft whereby the driven shaft is 10 reciprocated axially a distance sufficient to comminute chips developed by the drill, and a sun gear in mesh with the planet gear and driven from the drive shaft.

10. In a device of the class described having a stationary element, and a drive shaft and a drill carrying driven shaft journalled for simultaneous rotation and relative reciprocation, the combination of an annular cam member supported upon the stationary element and having a radial cam path thereon with a relief therein occupying an arc of less than 180, a follower device cooperating with the cam path including a lever having a follower upon an arm thereof engaging the cam path and means for translating the cam and follower action to an oscillation of the driven shaft whereby the driven shaft is reciprocated axially a distance sufficient to comminute chips developed by the drill, a differential transmission interconnecting the drive shaft and the stationary element including an intermediate gear carrying said follower device whereby the reciprocation of the drill is recurrent in stepped relationship with the rotation of the drill.

MILTON C. TAYLOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,656,388 Nielsen Jan. 17, 1928 1,995,027 Glassford Mar. 19, 1935 2,391,463 Kingsbury Dec. 28, 1943 

